O_3 photochemistry on O_3 episode days and non-0_3 episode days in Wuhan, Central China

摘要

Simultaneous field measurements of ozone (03) and its precursors were conducted at an urban site (Zi Yang, ZY) and a suburban site (Huang Pi, HP) in August 2018 in Wuhan, China. The observation results revealed that the mean levels of nitric oxide (NO), nitrogen dioxide (NO2), carbon monoxide (CO) and non-methane hydrocarbons (NMHCs) were higher at ZY than those detected at HP, while the opposite trend was observed for O-3 levels. Compared to non-O-3 episode days, higher levels of O-3 and its precursors (i.e. NMHCs, NO and CO) were observed on O-3 episode days at both ZY and HP. A chemical box model was used to investigate the O-3 photochemistry on O-3 episode days and non-O-3 episode days at ZY and HP, and the O-3 production was found to be dominated by the reaction of HO2 + NO at the two sites. In terms of O-3 destruction, OH + NO2 was the major contributor at ZY, while the highest contribution at HP was from the reaction of O(1D) + H2O. The net O-3 production rates increased significantly from non-O-3 episode days to O-3 episode days at both ZY and HP, indicating increased O-3 accumulation on O-3 episode days. In addition, the model simulation indicated that O-3 formation was controlled by volatile organic compounds (VOCs) at ZY, whereas O-3 formation was cooperative controlled by VOCs and NO at HP. Overall, these findings can provide valuable information on formulating and implementing O-3 control strategies in urban and suburban areas in China.